Information Technology Reference
In-Depth Information
Notice that this port can be a part of a group of two (2/1-2) or part of a group of four (2/1-4). An Ethernet
Bundling Controller (EBC) on the module causes these configuration limitations. Let's look at another
port.
Switch-A
show port capabilities 2/3
Model
WS-X5225R
Port
2/3
...
Channel
2/3-4,2/1-4
This port can be grouped into a group of two ports (2/3-4) or into a group of four (2/1-4).
Depending on the hardware, there might be additional restrictions. On certain modules
(WS-X5201 and WS-X5203), you cannot form an EtherChannel with the last two ports in
a “port group” unless the first two ports in the group already form an EtherChannel. A port
group is a group of ports that are allowed to form an EtherChannel (2/1-4 is a port group
in the previous example). For example, if you are creating separate EtherChannels with
only
two
ports in a channel, you cannot assign ports 2/3-4 to a channel until you have first
configured ports 2/1-2 to a channel, for the modules that have this restriction. Likewise,
before configuring ports 2/6-7, you must configure ports 2/5-6. This restriction does not
occur on the modules used for this document (WS-X5225R, WS-X5234).
Note
Because we are configuring a group of four ports (2/1-4), this is within the approved grouping. We would
not be able to assign a group of four to ports 2/3-6. This is a group of contiguous ports, but they do not
start on the approved boundary, as shown by the
show port capabilities
command (valid groups would
be ports 1-4, 5-8, 9-12, 13-16, 17-20, and 21-24).
Create the channel. To create the channel, use the command
set port channel <mod/port on
for each
switch. We recommend turning off the ports on one side of the channel using the
set port disable
command before turning on EtherChannel manually. This will avoid possible problems with
Spanning-Tree Protocol during the configuration process. Spanning-Tree Protocol could shut down
some ports (with a port status of errdisable) if one side is configured as a channel before the other side
can be configured as a channel. Because of this possibility, it is much easier to create EtherChannels
using PAgP, which we will cover in the section “ Using PAgP to Configure EtherChannel “ coming up
later in this chapter. To avoid this situation when configuring EtherChannel manually, we will disable
the ports on Switch A, configure the channel on Switch A, configure the channel on Switch B, and
then
re-enable the ports on Switch A.
First verify that channeling is off.
Step 6
Switch-A (enable)
show port channel
No ports channelling
Switch-B (enable)
show port channel
No ports channelling
Now disable the ports on Switch A until both switches have been configured for EtherChannel so that
Spanning-Tree Protocol will not generate errors and shut down the ports.
Switch-A (enable) s
et port disable 2/1-4
Ports 2/1-4 disabled.
[output from SwitchA upon disabling ports]
1999 Dec 15 00:06:40 %PAGP-5-PORTFROMSTP:Port 2/1 left bridg1
1999 Dec 15 00:06:40 %PAGP-5-PORTFROMSTP:Port 2/2 left bridge port 2/2
1999 Dec 15 00:06:40 %PAGP-5-PORTFROMSTP:Port 2/3 left bridge port 2/3
1999 Dec 15 00:06:40 %PAGP-5-PORTFROMSTP:Port 2/4 left bridge port 2/4
